A simple PHP snippet to verify authorisation via IP address. Supports wildcard/partial IP addresses.

ip_based_auth.php

<?php

$allowable_ips = array(
    '192.168.0.',
    '8.8.8.8',
);

$is_allowed = (bool) array_filter($allowable_ips, function($value) {
    return (substr($_SERVER['REMOTE_ADDR'], 0, strlen($value)) == $value);
});

if(!$is_allowed) {
    die('Denied.');
}